Case report: A 43-year-old man with T3 N2 M0 adenocarcinoma of the lower rectum was admitted for preoperative radiochemotherapy (RCT). Daily fractions of 1.8 Gy (planned total dose: 50.4 Gy) and concomitant chemotherapy consisting of 5-fluorouracil (5-FU), leucovorin, and mitomycin C (MMC) were administered. On day 10, the patient developed abdominal pain and massive diarrhea. Computed tomography, endoscopy, histopathologic and serologic tests revealed severe colitis confined to the upper abdomen and most probably related to 5-FU. Unexpectedly, the bowel inflammation was restricted to areas not irradiated. 4 months later, during the course of disease, relapse with pulmonary metastases occurred. A palliative chemotherapy with 5-FU, oxaliplatin, and leucovorin was started. Again, the patient suffered from severe diarrhea and dose reduction was necessary.
Discussion: It was speculated that in the early phase of RCT the well-known anti-inflammatory nature of low-dose radiation prevented exacerbation of colitis. To the authors' knowledge, this observation has not been published before. With respect to the current literature and the clinical findings it is discussed that both increased leukocyte/endothelial cell adhesion and altered release of reactive oxygen species or inducible nitric oxide synthase (iNOS) may play a role in 5-FU-induced colitis.
Conclusion: This observation led to the hypothesis that the anti-inflammatory effect of low-dose irradiation may attenuate 5-FU-induced colitis in the very early phase of RCT. It appears worthwhile to separate side effects of RCT into radiation- and chemotherapy-induced effects, which requires a detailed diagnostic work-up. This differentiation has an impact on planning individual therapy: the authors did not saw conclusive evidence of an increased radiosensitivity but chemosensitivity in their patient and therefore continued radiotherapy. This assumption was confirmed when the patient received palliative 5-FU-based chemotherapy due to pulmonary relapse, and again, severe diarrhea occurred.